Control mechanism for electric tools



Aug. 17 1926.

. J. J. GEBHARDT CONTROL uzcamlsm FOR ELECTRIC TOOLS Filed A til 13, 923/326 p Patented Aug. 17, 1926.

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com-non MECHANISM FOR mic: moons:

mum meduwuaia 1m. 'smmm; .mpsoi Theinvention pertains to electric toolssuch as drills, hammers,- etc. and hasforits aim t Q PIOVlSlOIlOf acontrolling: mechanism* of advantageous:

g: charaoten for toolsoff this typu Portable electrio tools newoommonlysinv use are uipped with wswitch mechanism for oontro ling theoperation, which requires.

a manual operation bothvfovwtting the tool 10' inc ation and forstopping-it: Because of t distinct manual operatiom required? forstopping the tool; the new frecgzently negleots tmcut of! theourrentwhen. lays the tool aside so thatdtcontinues to operate w idly.This-results in unnecessary wearand tea'r'and also presents 1 source ofdanger:

to the operator and his" fellow workmen. Moreover,- mrder someoomlitions it' is very necessary thmt the tool hm brought to: an 20'ihstknt stop, but inthe umeof the tools in common use, as abovementimedl-inmudl as the stoppage requires= the distimt. operation of theswitch, considerable: time may eltppebefore it is possible to-bring;the=tool 88' to rest, and in this-time serious-injury may resultto the operator as well ias to 'the tool. Toovercome the disadvantagesresulting fiom the common type'orf control n'ism; itis desirable toemploy w switch 80 which automatically breaksth e circuit when theoperator releases the switch operating: member. In some instlmms;However, the.

0 fitter-army desire-to look the switch in I c osedosition se thut theopereton will be w relieve -of the necessity of holding the switclflosedi The object of invention is to provide a. controlling mechanismincluding a switch whioktends atall timwto-move'intoopen en position,and means associated with the switchwperating member and arranged sothatit may be set' to eutomaticelly look" the switch in L closed" positionon to permit the switch to move automatically" into its 45' openposition. p p

A further and incidental ohj eeta-is'wo'prm vide' a switch mechanismaesoeiadzed' withl' the handle of an electric tool and heving a lockingmeans which is especially adapted 00 for convenient opemtiom to releasethe switch instantly w en'occasion-r ires;

The 'ob yeets of the invention t s generally stated together with otherand I email liu'yadvantages flI'G-fittflillfid? by the: 0011-- uilfustrated' in the moom'panying oriable grinders, v.

drarwingss forming; part; hereof. l have: illustra'ted; blltTOllB. formofimy inventiomiit being contemplated. that various changes may be madeby thosei skilled: in the: artl withouti departingafrnm the spirit. andscope: of? the: inventionas expressed in! the" ape pendedi claims-: i p

'Figures l' ofithe drnwings is a sidesel'evm tionalz View of anelectric: drill equipped: with a controlling." mechanism; constructed in1 accordimce with my; inventiomn Ei'g. 21s afragmentary: underside viewofithe" con-r trolling mechanism as; applied. to the? side" of thedrill: Fig: 3.is-1a frontrsideelevationali View oil the control devicesFig: 4 is an elevational :view: partly. im -section look; ing: into theinterior ofrtheswitoh; casing:

I have selected? for purposes :ofillustrm-Q tionv a portable: electricdrill? comprising at casing 7 enclosing an electric. motor 8: and:suitable operative connections. (not shown): the. motor and the drillchuck. 9;. 10 designates ai=handle\a/t' the upper: end of the casing,and 11' and 12 designate? side: handles extendin radially from a the"casing. 7 at diametrica y opposite! sides thereof; The handle 11 issuitably iastemddmaho'ssx or enlargement 13'; and the handle: 12: is":carried 1 by; wlrousing- '14 fDII' the switch? dese: ignatedgenerallybythei minim-e145; (Fig. 4): Sai housinggi's-suitably securedtothe side oithe casing 7 as hyimeans-of screws 16'. Electric currentpassesto" motor 8 through conductors 17, one of which passes intoandoutwf the switch: housing =14! for connection with the switchierminalsin: a weil knowmmmnerr The stvitch 15- hereinr showm comprises mplunger-'18 slidwble' in"a bracket l and con meted by means of aco'iIed' temiOn spring 2O with arpi-voted yoke 21 constituting-themovable switch conta'ctz A pair of station my contacts 22 (one onlybeing herein shown) is mounted upon an insulated base? plate 23and-connected with: binding post's 24towhich extend the conductors 17.A0 coiled compression spzing 25" normally h oldssthe plunger 18' in its=outermost: position in' tlr'e'bracket 19, andflimth'e reciproce tion-ofthe plunger the swingingcontnetfil 195 operates with a" sneppin f actioninto and out' of engagement witlr t "e'" stationary contests 22.

To; operate the plunger 18* to close the l switeh; a lever 261s at 27iuth'e.

lower portion of the housing 14 near the forward edge thereof. Thislever operates in a slot 28 formed in the lower side or edge wall of thehousing, and the free end of the lever has a foot or bearing portion 329which rests slidably upon a head 30 of insulating material carried bythe free end of the plunger 18.

It will be seen that in order to maintain the circuit closed theoperator, with the construction thus far described, must retain his holdupon the switch lever 28 which he can conveniently do because of theassociation of the switch with the handle 12. In Fig. 1 I have shown inbroken lines the switch lever as applied to the handle 10. In eithercase, the lever is held in its closed or inward position by a linger orthe thumb of the hand upon the handle, and it will be apparent thatimmediately upon the release of the lever the tool will. come to rest.lVith this arrangement the tool is capable of operation with maximumsafety to the operator, his co-worl ers and to the tool itself. However,in order that the tool may be capable of operation so as to release bothhands of the operator for other work and at the same time provide forthe opening of the motor circuit with maximum ease and rapidity, Iprovide a locking means for the switch comprising a retaining or hookmember 31 pivoted at 32 near the free end of the lever 26 and on an axisparallel with the pivot 27 for said lever. The pivot 32 may be mounted,in an enlargement or rib 33 upon the lower forward side of the housing,the rib being suitably cut away or notched at 3 t to receive theretainer member and permit of its swinging movements to be presentlydescribed.

The lower end of the member 31 has a portion 31 extending rearwardlysubstantially at right angles to the main portion of the member andadapted to engage with ashoulder 35 formed by the lower end of a plate36 which is fast upon the free end of the switch lever 26. Since thelatter is made preferably of aluminum, the plate 35 is formed separatelyand made of steel. or other suitable wear-resisting metal. A coiledexpansion spring 37 is interposed between the retainer member 31 and theforward side wall of the switch housing so as to tend to force the hook331 against the plate 36 on the lever 26, whereby when the latter isoperated to close the switch, the hook will snap into engagement withthe shoulder 35 to lock the switch lever and hence the switch in closedposition. The spring 37 preferably encircles a pin 38 carried by theretainer member 31 and it enters a socket 39 in the forward side of thehousing.

It will be observed that the retainer mem-.

ber 31 extends upwardly almost flush with the upper side of the housingand along the forward face thereof. The member is thus -in convenientposition to be tripped by the hand of the operator on the handle 12,whereby to release the switch for movement into its open position. Ihave found in practice that the switch may be released much more rapidlythan is possible with switches of the non-automatic type which require adistinct manual operation to open the circuit. Thus with the presentconstruction a mere touch upon the free end of the retainer member issutlicient to release the lever 26 for outward movement.

If now it is desired to render the retaining or locking meansinoperative, this may be done by means of a small slide plate 40 mountedupon the underside of the rib 33. Said plate is secured upon the rib 33by means of a screw ll, being slotted centrally thereof to receive thescrew. At one side of the slot the plate is extended forwardly to form afinger 42 which is adapted to enter between the retainer member 31 andthe adjacent wall of the housing, thus constituting an abutment for theupper portion of the retainer member to prevent it from swinging intoengagement with the shoulder 35 under the action of the sprin 37. Theplate has a central hump 40 whic is so positioned with respect to thescrew 41 as yieldingly to resist sliding movement of the plate intoeither extreme position.

It will be seen that by the provision of the retaining means which Ihave provided, the tool is capable of operation with the controllingmechanism semi-automatic, to provide a. maximum safeguard againstinjury, or with the control mechanism automatically locked in positionto maintain the circuit closed but permitting the instant release of theswitch for movement into open position. Thus, in either event, thepossible injury to the operator and to the tool is minimized.

From a manufacturing standpoint the re taining device can be applied tothe control mechanism at a practically negligible cost and theconstruction is such that it will not wear out readily nor requirefrequent repair.

I wish especially to point out that the invention is not limited to theapplication of my improved retaining device to switches of the specificcharacter herein illustrated and described, nor to switches located uponthe side of the tool as in the present instance, for it is contemplatedthat it may be used wherever the switch is located whether it be uponthe side of the tool, in the handle 10 or elsewhere.

I claim as my invention:

1. In an electric tool, the combination of a switch having a swingingcontact, a reciprocable operating member having a resilient connectionwith said contact to swing it, a spring tending to resist the movementof said operating member to move said contact into closed position, anoperating lever engaging said plunger to 0 rate it, and means or lockingthe lever an thereby the switch in closed position.

2. In an electric tool, the combination with a control mechanismcomprising a switch having a swinging contact member, a plungerresilient] connected with said memer, a spring ten ing to resistmovement of said plunger in one direction, an operating lever pivoted atone end and operatively associated at its other end with said plunger,and means associated with said lever adapted to engage therewithautomatically whereby to lock said swinging contact member in closed oroperative position.

3. In an electric tool, the combination with a control mechanismcomprising a switch having a swinging contact member, a longerresiliently connected with said memr a spring tending to resist movementof said plunger in one direction, an operating lever pivoted at one endand operatively associated at its other end with said plunger, meansassociated with said lever adapted to engage therewith automaticallywhereby to lock said swinging contact member in closed or operativeposition, and means for holding said retaining member in inoperativeposition; 4. The combination in an electric control mechanism of anoperating member, and a device for locking the operating member in apredetermined osition, spring means tending to move the device in onedirection, and a slide plate movable into engagement with the lever toprevent movement of the lever by such spring means.

5. The combination in an electric control mechanism of an operatingmember, and a device for locking the operating member in a redeterminedposition, spring means tendmg to move said device in one direction, anda slide late movable into engagement withthe device to prevent movementthereof by such spring means, said slide plate having means forresiliently holding it in either operative or inoperative position.

In testimony whereof, I have hereunto affixed my signature.

JAMES J. GEBHARDT.

